Method of spinnerette cleaning during the preparation of inorganic oxide monofilaments



May 21, 1968 R. J. LOCKHART METHOD OF SPINNERETTE CLEANING DURING THEPREPARATION OF INORGANIC OXIDE MONOFILAMENTS Filed Jan. 21, 1965 3 :588:6 wm cwE 62989 we: 2:2 2:2; E E m 3 4 mtmtmccfim INVENTOR Robert J.Lockhart mE m 82mm co om ATTORNEY United States Patent METHOD OFSPINNERETTE CLEANING DURING THE PREPARATION OF INORGANIC OXIDEMONOFILAMENTS Robert .I. Lockhart, Shaker Heights, Ohio, assignor toHorizons Incorporated, a corporation of New Jersey Filed Jan. 21, 1965,Ser. No. 426,875 5 Claims. (Cl. 264-39) ABSTRACT OF THE DISCLOSURE Aprocedure for removing the accumulations which form in the vicinity ofthe extrusion orifices of a spinnerette through which inorganic oxidefilaments are extruded from a viscous concentrate, in which the faceportion of the spinnerette is cleared of any accumulations by immersingthe face portion of said spinnerette in a succession of liquids whileextrusion takes place to assist in physically detaching theaccumulations from the spinnerette face.

This invention relates to the spinning of monofilame'nts of inorganicpolymers of the type described in French Patent 1,316,535 whichcorresponds to United States Patent 3,180,741 issued Apr. 27, 1965, andin United States patent application 252,083 filed Jan. 17, 1963 whichissued on Mar. 28, 1967, as United States Patent 3,311,689 and thedisclosures of which are incorporated herein by reference.

Each of the patents describes the preparation of a liquid concentratefrom which monofilaments of inorganic oxides may be dry spun, into airor other gaseous atmospheres, the preparation of said concentrateforming no part of the present invention which is directed to aprocedure for treating the spinnerette orifices in order to improve thecontinuity of the extrusion process.

When producing filaments of inorganic oxides by the dry spinningprocesses described in the above noted patents, it has been founddifficult to produce continuous filaments for any extended intervals oftime, due principally to the accumulation of spining solution on partsof the face of the spinnerette until the accumulated material fallsunder the influence of gravity. When these accumulations break loosethey often whip around and snap the filaments forming from adjacentunobstructed spinnerette holes. In addition, accumulations attached tothe spinnerette hang down and catch or tangle emerging filaments. Asimilar phenomenon is experienced in melt spinning of synthetic polymerfilaments as described, for example in United States Patent 3,129,272which also describes procedures for minimizing the formation of suchaccumulations in dry spinning, such as blanketing the face of thespinnerettes uniformly and completely with an inert gas. Such aprocedure adds considerably to the expense and requires extremelycareful control when applied to dry spinning of inorganic oxidefilaments.

Various methods of overcoming the formation of such accumulations whichhave been attempted in dry spinning of inorganic filaments includeapplication .of surface coatings to the spinerettes to retard thespreading of liquids on the exit side of the spinnerettes and mechanicalpolishing of the spinnerette face to remove any scratches and toeliminate any surface discontinuities which might favor the utilizationand propagation of such accumulations.

When extruding inorganic oxide monofilaments, coatin g the spinnerettewith silicone oils, silanes, waxes, Teflon, or other lubricants did noteliminate the formation of the undesired accumulations, which appearedon the spinnerettes just as if no coatings had been applied.

3,384,69fi Patented May 21, 1968 Examination of new unused spinnerettesrevealed an overall pattern of parallel scratches apparently from thefinishing operations incidental to the manufacture of the spinnerettes.Examination of the same spinnerettes after use revealed that they hadbecome much more scratched, owing to the softness of the platinumrhodium alloy of which the spinnerettes are fabricated. Polishing thespinnerettes to a mirror finish noticeably improved the process, but theeffect was only temporary, since the scratches formed again duringnormal handling and cleaning operations.

The principal objects of this invention are to provide a simple andeffective Way to delay or prevent the formation .of accumulations on thespinnerettes during the dry spinning of inorganic oxide monofilamentsand to provide a simple and effective way to remove such accumulations,if and when formed, without serious interruption of the spinningprocess.

Briefly, in accordance with the present invention, these objects wereachieved by placing a container of a suitable liquid under thespinnerette orifices, and then moving the container or spinnerettesrelative to one another so as to immerse the entire outer face of thespinnerette cup in the liquid, and keeping the two in contact for a timesuffieient to clear the faces of the spinnerettes of anyaccumulated'fresh or partially dried spinning solution.

One liquid found to be suitable was warm water, but it was also foundthat after the water had cleared the spinnerette holes and face, itwould remain on the face of the spinnerette after the container wasmoved away, and would be in the form of a large drop, which remainedlong enough to permit the emerging inorganic .oxide dope to recoat thesurface. The disadvantage was overcome by removing the container ofwater and replacing it as promptly as possible with a container of avolatile liquid in which the spinning solution is insoluble. Acetone isone such liquid and when the container of acetone was removed, theacetone evaporated and the face of the spinnerette remained clearpermitting the continuous spinning of inorganic filaments for hours ascompared with fractions of an hour prior to this invention.

The procedure just described is shown schematically in the drawingsaccompanying this application in which FIGURE 1 shows a spinnerettebearing an accumulation of spinning solution sufficient to impairsatisfactory operation of the process;

FIGURE 2 shows the spinnerette of FIGURE 1 shortly after it was immersedin warm water, and just after the accumulation has dropped off of thespinnerette permitting the resumption of extrusion through thespinnerette orifices;

FIGURE 3 shows the spinnerette immediately after the body of warm waterhas been removed from the spinnerette leaving one residual drop of Watersuspended from the spinnerette face;

FIGURE 4 shows the spinnerette after it has been immersed in a volatileliquid; and

FIGURE 5 shows the spinnerette after the volatile liquid has evaporatedand shows filaments of inorganic oxide as they are extruded into air.

Other liquids which may be used in place of warm water F.) to clear thespinnerettes of accumulated spinning solution included acetic acid,either as glacial acetic acid or as aqueous solutions of the acid and itappears that the accumulation-clearing liquid could be any liquid inwhich the spinning solution is at least partly soluble and which did notreact chemically or corrosively upon the spinnerette.

Other volatile liquids which were used in place of acetone werechloroform, carbon tetrachloride, ethyl ether and cyclohexane each ofwhich evaporates quite rapidly 3 from the face of the spinnerette oncethe bath is removed from the spinnerette.

It has been found that the best results are obtained by using Warm Waterfor the spinnerette clearing liquid and a water miscible liquid such asacetone for the water removing, spinnerette drying liquid.

Having now described preferred embodiments of the invention it is notintended that it be limited except as may be required by the appendedclaims.

I claim:

1. In a process in which a liquid concentrate suitable for theproduction of an inorganic oxide monofilament is extruded into airthrough a spinnerette plate having a plurality of extrusion orificestherein, the improvement which comprises: clearing away any accumulationfrom the face of said spinerette plate by immersing the face portion ofsaid spinnerette in a first liquid selected from the group consisting ofwarm water, aqueous and glacial acetic acid in which said accumulationsare at least partly soluble; withdrawing said spinnerette from saidfirst liquid while extruding said inorganic oxide monofilament producingconcentrate through said spinnerette face;

4. promptly after withdrawing said spinnerette from said first liquid,immersing said face portion of said sipnnerette in a volatile secondliquid in which said first liquid is soluble to remove any residue ofsaid first liquid from said spinnerette face; and thereafter withdrawingsaid spinnerette from said volatile second liquid while extruding saidconcentrate through said spinnerette face and continuing said extrusionwhile any residual volatile second liquid evaporates into thesurrounding atmosphere.

2. The process of claim 1 in which the'first liquid is warm Water andthe second liquid is acetone.

3. The process of claim 1 in which the second liquid is a volatileorganic liquid.

4. The process of claim 1 wherein the inorganic oxide is alumina.

5. The process of claim 1 wherein the inorganic oxide is zirconia.

No references cited.

JAMES A. SEIDLECK, Primary Examiner.

H. MINTZ, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,384,690 May 21 1968 Robert J. Lockhart It is certified that error appearsin the above identified patent and that said Letters Patent are herebycorrected as shown below:

Column 1, line 42, "spining" should read Column 4, line 19, cancel "Noreferences cited." and insert References Cited UNITED STATES PATENTS1,901,658 3/1933 Ladrette --26439 3,180,741 4/1965 Wainer et a1 --106-393,311,689 3/1967 Kelsey -264-210 Signed and sealed this 7th day ofOctober 1969.

(SEAL) Attest:

Edward M. Fletcher, Jr.

Attesting Officer WILLIAM E. SCHUYLER, JR.

Commissioner of Patents spinning

